Special equipment: a deep-frying thermometer
For the tomato sauce: Heat the olive oil in a large skillet or saucepan over medium-high heat until hot. Add the onion and cook until softened, translucent and slightly brown on the sides, about 2 minutes. Add the garlic and cook until fragrant, about 30 seconds more. Pour in the tomatoes. Bring to a simmer and cook, stirring occasionally, until the flavors combine and the liquid begins to reduce slightly, 10 to 15 minutes. Season with salt and pepper. Keep warm over low heat until ready to use.
For the cauliflower: Meanwhile, trim the base of the core from the cauliflower, then cut the head into 1-inch-thick slices (steaks). Cut any florets that fall off into 1-inch pieces. Sprinkle 1/4 teaspoon each salt and pepper over both sides of the cauliflower.
Whisk together the flour, garlic powder, 1 teaspoon salt and 2 teaspoons black pepper in a shallow bowl. Whisk together the milk and eggs in a second shallow bowl. Whisk together the breadcrumbs and Parmesan in a third shallow bowl. One at a time, dredge the cauliflower steaks and 1-inch pieces first in the flour mixture, then in the egg mixture and then into the breadcrumb mixture, pressing firmly to coat. Transfer the breaded cauliflower to a rack on a rimmed baking sheet.
Set another rack on a rimmed baking sheet. Heat about 1 inch of vegetable oil in a deep cast-iron skillet or Dutch oven over high heat until a deep-frying thermometer registers 350 degrees F. Fry the cauliflower steaks one at a time with some of the smaller pieces, flipping after about 1 minute and then flipping a few more times until all sides are equally cooked, until dark golden brown, about 5 minutes (return the oil to 350 degrees F between each batch). Transfer the finished cauliflower to the rack on the baking sheet and immediately sprinkle lightly with salt.
Preheat the broiler.
Add the cauliflower to a 9-by-13-inch baking dish in a single layer or slightly overlapping. Pour the tomato sauce over the top and sprinkle with the mozzarella. Broil until the cheese is golden brown and bubbling, 3 to 5 minutes. Garnish with torn basil leaves. Serve hot.
Copyright 2017 Television Food Network, G.P. All rights reserved.